1. Field of the Invention
The present invention relates to an inspection method of a secondary battery and a manufacturing method of a secondary battery. More specifically, the present invention relates to a method for inspecting whether or not minute short-circuit occurs in a secondary battery.
2. Description of Related Art
A secondary battery such as a lithium-ion secondary battery has a lighter weight and a higher energy density in comparison with existing batteries, and is preferably used as a vehicle-mounted high-output power supply or the like. In the manufacture of such a battery, generally, an electrode body is first formed by use of a positive electrode and a negative electrode, and a battery is assembled by use of the electrode body and an electrolyte. Then, after the battery thus assembled is subjected to predetermined initial charge and aging, inspections before shipment, such as battery capacity check and self-discharge inspection, are performed thereon. The self-discharge inspection is performed such that, after the secondary battery is adjusted to a predetermined state of charge (SOC), the secondary battery is left to stand for a given period of time, and a voltage change during the leaving (self-discharge) is measured. Then, based on a measurement result obtained herein, it is determined whether or not minute internal short-circuit occurs in the secondary battery. As a technique related to this, Japanese Patent Application Publication No. 2011-069775 (JP 2011-069775 A) describes an inspection method performed in such a manner that: a secondary battery is charged to a first SOC and then left for stand (aging) for a predetermined time; subsequently, the secondary battery is discharged to a second SOC, which is lower than the first SOC; and it is determined whether or not minute short circuit occurs in the secondary battery under a temperature lower than a predetermined temperature.